Anaerobic treatment of high-sulfate wastewater and substrate interactions with isopropanol

Modified biological methane-potential tests were used to study the treatment of wastewater with a chemical oxygen demand (COD) concentration of 40,000 mg/L and a sulfate concentration of 5,000 mg/L. The effects of wastewater concentrations on biodegradation and substrate interactions between sulfate reducers and methanogens were studied. Isopropanol (IPA) degradation was studied since isopropyl acetate was the major organic component in the wastewater. Six sets of batch tests were done, including a series of tests with varying concentrations of wastewater; wastewater and glucose; glucose and sulfate; IPA; IPA and glucose; and IPA, glucose, and sulfate. Sulfur and electron balances were used to analyze data to determine the extent of biodegradation from both methanogenesis and sulfate reduction. IPA did not appear to be inhibitory to methanogenesis or sulfate reduction. In comparison to glucose, the presence of wastewater or isopropanol stimulated greater sulfate-reduction efficiency. Evidence for IPA degradation was observed, and IPA degradation was stimulated in the presence of sulfate. Continuous feed-reactor results corroborated batch-test observations.